Development of the coronary vessels is one of the most critical events in the formation of a functional heart. Proper assembly and patterning of the coronary system is essential for the continued growth of the developing heart and as well as maintenance of cardiac function in the infant and adult. Coronary development is a unique process of blood vessel formation, and appears to be conserved among vertebrate hearts (including human) with coronary vessels. While several groups have described coronary development and many genetic mutations are known to disrupt coronary vessel formation, surprisingly little is known about the underlying related projects and three cores focused on elucidating the cellular and molecular mechanisms that regulate the proper differentiation and patterning of the coronary system. Our proposed studies will test our hypothesis concerning the recruitment of progenitors to the coronary system. Our proposed studies will test our hypothesis concerning the recruitment of progenitors to the coronary system, their movement to and within the heart, their differentiation into vascular endothelial and smooth muscle cells and their patterning into a functional vascular bed. Our data will provide insight into the basic mechanisms governing coronary vessel development and an understanding of anomalous vessel formation and patterning that is so deleterious to the function of infant and adult hearts. The relationship of the process to our aims is given.